Set MaxResults if it is not set

[nckturner]

• EC2 pagination doesn't work if MaxResults is not set
• Only set if InstanceIds isn't set.

What type of PR is this?

Uncomment only one, leave it on its own line:

/kind bug

What this PR does / why we need it:
The describeInstances API doesn't paginate unless maxResults is set.
Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:
/hold

Does this PR introduce a user-facing change?:

Ensure pagination of EC2 describeInstances calls

[wongma7]

kubernetes/kubernetes#102927 this updated the cache to have a ttl of just 10 minutes. Seems like a very bad idea if we are trying to optimize our calls.

[nckturner]

/unhold

[wongma7]

do you mind double checking that describeAllInstancesUncached

cloud-provider-aws/pkg/providers/v1/instances.go

Line 153 in 58bc609

func (c *instanceCache) describeAllInstancesUncached() (*allInstancesSnapshot, error) {

ultimately calls this function? I am confident in my ctrl+clicking skills but just want to make 100% sure that we're covering all calls given that there are quite a few layers (describeAllInstancesUncached, describeInstances lowercase, DescribeInstances uppercase, sdk go's DescribeInstances uppercase...

[wongma7]

describeAllInstancesUncached calls c.cloud.describeInstances (c is for cache)

cloud-provider-aws/pkg/providers/v1/instances.go

Line 159 in 58bc609

instances, err := c.cloud.describeInstances(filters)

cloud-provider-aws/pkg/providers/v1/aws.go

Line 5002 in 58bc609

func (c *Cloud) describeInstances(filters []*ec2.Filter) ([]*ec2.Instance, error) {

c.cloud.describeInstances calls c.ec2.DescribeInstances (now c is for cloud)

cloud-provider-aws/pkg/providers/v1/aws.go

Line 5007 in 58bc609

response, err := c.ec2.DescribeInstances(request)

cloud.ec2 is a v1.EC2 interface

cloud-provider-aws/pkg/providers/v1/aws.go

Line 334 in 58bc609

type EC2 interface {

and the "real"/non-mock implementation of it by awsSdkEC2 is

cloud-provider-aws/pkg/providers/v1/aws.go

Line 964 in 58bc609

func (s *awsSdkEC2) DescribeInstances(request *ec2.DescribeInstancesInput) ([]*ec2.Instance, error) {

which calls s.ec2.DescribeInstances (now ec2 is an aws-sdk-go ec2.EC2 not a v1.EC2/awsSdkEC2)

cloud-provider-aws/pkg/providers/v1/aws.go

Line 731 in 58bc609

ec2 *ec2.EC2

[wongma7]

/lgtm

[k8s-ci-robot]

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